KR101592698B1 - All-solid state secondary battery using hybrid electrolyte - Google Patents

Abstract

The present invention relates to a method for solving the problem of contact between electrodes of solid electrolytes, which has advantages of solid electrolytes by using electrolytes in a double-walled all-solid state battery.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an all-solid secondary battery using hybrid electrolytes,

The present invention relates to a method for solving the problem of contact between electrodes of solid electrolytes, which has advantages of solid electrolytes by using electrolytes in a double-walled all-solid state battery.

At present, liquid electrolytes are mainly used in secondary batteries. Many attempts have been made to replace such electrolytes with solid electrolytes.

When a solid electrolyte is used, it is advantageous from the viewpoint of safety first. Most liquid electrolytes are flammable and have a risk of explosion, whereas solid electrolytes are not flammable and stable at high temperatures and pressures. In addition, the lifetime characteristics of the battery can be improved, and the energy density can be increased because stacking is possible in a stacked form.

The electrolyte plays the role of ion conduction, and the solid electrolyte has a contact problem due to its phase property called solid. In the case of a liquid electrolyte, it seeps into the electrode to form an electrode material and a conduction path, but the solid electrolyte must take this conduction path into account when designing the electrode. Now, it is known that a method of forming an electrode by pulverizing a solid electrolyte and mixing it with an electrode material (FIG. 1) and a method of manufacturing an electrode by a thin film (FIG. 2) are known.

In the case of the pulverized solid electrolyte, the contact ratio is inferior to that of the liquid electrolyte and there is a problem that the interfacial resistance is increased.

In other words, in the case of a solid electrolyte thin film, it is difficult to form a high-density battery with an increased loading amount. Accordingly, the present invention aims at solving the problem of insufficient contact within the electrode of the solid electrolyte while maintaining the advantages of the solid electrolyte by using a double electrolyte in the all-solid-state battery.

On the other hand, as a similar technique, a technology (JP 2009-225231, see FIG. 4) for forming a sulfide solid electrolyte layer containing a polymer (JP 2008-194550, see FIG. 3) and a technique of coating a solid electrolyte with a polymer to improve contact ).

However, such a technique can not provide a solid electrolyte having a desired level of contact, and in terms of its constitution, essentially no double electrolyte is used in the case of electrons. In the latter case, the polymer is used as a binder, .

The present invention attempts to overcome the technical limitation that a contact ratio of a pulverized solid electrolyte is inferior to that of a liquid electrolyte and that a solid-electrolyte secondary battery having a high loading can not be constructed due to an increase in interfacial resistance.

That is, the present invention has advantages of a solid electrolyte by using an electrolyte in a double-walled electrolyte in an all-solid-state cell, and solves the problem of contact of the solid electrolyte with an electrode.

The present invention relates to a pre-solid secondary battery comprising a negative electrode, a positive electrode and a solid electrolyte stacked therebetween, wherein the negative electrode and / or the positive electrode is composed of an active material, an electron conduction material and a gel polymer electrolyte, The present invention provides a pre-solid secondary battery wherein the material is incorporated and dispersed in a gel polymer electrolyte, the cathode and / or the anode contains no separate binder, and the gel polymer is a gel polymer containing a lithium salt .

The effects of the present invention are as follows.

1) it retains the advantage of choosing a solid electrolyte.

That is, the energy density can be improved because the lithium secondary battery is stable at a high temperature and a high pressure as compared with a liquid electrolyte, has excellent lifetime performance of the battery, and can be stacked in a stacked form.

2) solved the insufficient contact problem of the solid electrolyte inside the electrode of the pre-solid battery.

That is, the amount of contact between the electrolyte and the electrode material in the electrode is increased as compared with the technique using the conventional solid electrolyte, and the internal resistance of the electrode is decreased to increase the capacity of the battery.

As a result, it is possible to form electrodes of high loading and high density as compared with a technique using a conventional solid electrolyte thin film.

3) The capacity of the electrode increased through binder exclusion.

That is, since the gel polymer electrolyte can replace the role of the binder, the binder can be excluded, and thus the amount of the active material used can be increased, resulting in an increase in the battery capacity.

1 is a schematic view of a conventional solid electrolyte crushing electrode.
2 is a schematic view of a conventional solid electrolyte thin film electrode, which relates to a method of expanding the contact area by forming a three-dimensional electrolyte layer.
3 is a representative view of JP 2008-194550.
4 is a representative view of JP 2009-225231.
5 is a schematic diagram of an all solid-state battery using the heterogeneous electrolyte of the present invention.
Figure 6 is a schematic diagram of an ADM instrument.

The present invention relates to a pre-solid secondary battery comprising a negative electrode, a positive electrode and a solid electrolyte stacked therebetween, wherein the negative electrode and / or the positive electrode is composed of an active material, an electron conduction material and a gel polymer electrolyte, Solid secondary battery in which the material is incorporated and dispersed in a gel polymer electrolyte, the cathode and / or the anode does not contain a separate binder, and the gel polymer is a gel polymer containing a lithium salt ).

The lithium salt should be well dissociated into the organic solvent and contain lithium ions in the dissociated state. The lithium salt is typically _{LiBF 4, LiClO 4, LiPF 6} , LiAsF 6, LiCF 3 SO 3, LiN (SO 2 CF 3) 2, LiN (SO 2 C 2 F 5) 2, LiC (SO 2, CF 3 ) ₂ , LiB (C ₂ H ₅ ) _4, or a combination of at least one of them.

The gel polymer may be a physical crosslinking gel or a chemical crosslinking gel, and may be a homogeneous gel or a heterogeneous gel.

The gel polymer includes an acrylate crosslinking agent, a carbonate-based or ether-based solvent, and a lithium salt. Initiators may be included depending on the curing method. Physical crosslinking gels form gels through ionic or hydrogen bonds of one or more polymers. Chemical crosslinked gels constitute gels by copolymerization between polymers.

The pre-solid secondary battery may be a lithium sulfur secondary battery, wherein the active material is sulfur, the electron conductive material is a carbon body such as acetylene black series, carbon nanotube, or graphene, and the content of the gel polymer in the anode and / May be 10 to 30% of the total electrode mass, and a lower ratio within the ion conduction path is preferable.

The pre-solid secondary battery may be a lithium ion battery. The active material may be LiCoO ₂ , LiNiO ₂ , LiNi _x Co _y Mn _z O ₂ ternary system, LiMe _x Mn _{1 - x} O ₄ , LiFePO ₄ Or a mixture of at least one of these materials. The electron conductive material may be a carbon material such as acetylene black series, carbon nanotubes, graphene, or a mixture of at least one of them. The content of the gel polymer in the cathode and / It may be 10 to 30% of the electrode mass, and a lower ratio within the ion conduction path is advantageous.

The solid electrolyte may be a NASICON-type, a Garnet-type, a Perovskite-type, a LiPON-type or a Thio- -LISICON-type), preferably 10 to 1,000 mu m, and may be laminated in a film form, a sputtering or coated form, or a powder form.

The cathode and / or the anode are preferably cast to 100 to 200 mu m.

A method of producing a pre-solid secondary battery containing the heterogeneous electrolyte of the present invention is as follows.

The electrode material (active material) of the anode and / or the cathode, the electron conduction material (carbon material) and the gel polymer electrolyte are mixed. Here, a separate binder is excluded.

The gel polymer is suitable for 10 wt% of the total electrode mass. When the conventional liquid electrolyte is used, the liquid electrolyte permeates into the electrode and is 10 to 20 wt% of the electrode. It is possible to manufacture an electrode for loading the active material by eliminating the binder while having an electrolyte ratio similar to that of the liquid electrolyte. The use of a solid electrolyte that compensates for disadvantages (safety, volume, etc.) when using a liquid electrolyte is solved, but the ion conduction path formation inside the electrode, which is the biggest problem in using a solid electrolyte, is solved.

The ratio of the electrode material (active material) and the electron conductive material (carbon material) varies depending on the type of the battery.

The ratio of sulfur: carbon = 3: 1 is applied to the lithium-sulfur battery, and the ratio of active material: carbon = 45: 1 is applied to the lithium-ion battery.

The solvent for mixing the constituent materials may be NMP, and the amount of NMP is preferably 10 times as large as that of the gel polymer.

You can mix them using triggers and mix them for more than 20 minutes. Various mixing methods such as a fliniter mill, a ball mill and the like may be used as the mixing method.

To prepare an electrode, a slurry in which materials are mixed on a substrate (the active material and the electronic conductive material are mixed and dispersed in a gel polymer electrolyte) is cast using a doctor blade. Al can be used as the base material, and the casting thickness is 100 to 200 mu m, preferably 150 mu m. The fabricated electrode is dried at 80 ° C for one day.

Next, a solid electrolyte membrane is produced. Aerosol Deposition Method (ADM) can be used for the formation of the solid electrolyte membrane, which is a process of forming a high-density thick film at room temperature by rapidly colliding a submicrometer-sized raw powder through a nozzle. Therefore, since a high-density thick film can be formed even at room temperature, a ceramic raw material can be used, and the stoichiometric ratio of the raw material can be maintained in the thick film.

The size of the raw material powder of the solid electrolyte membrane is preferably 1.5 占 퐉 in average diameter.

The thinner the solid electrolyte membrane (100 탆 or less), the better the ion conductivity. However, in terms of battery stability, the solid electrolyte membrane needs to be a thick film (~ 1,000 μm). It is known that ADM (see FIG. 6) is unique to make a ceramic film with a thick film in mm.

When a ceramic solid electrolyte is used, there are the following advantages.

Ceramic solid electrolytes are excellent in ionic conductivity as electrolytes. It is now known to have an ionic conductivity of up to 10 ^-2 S / cm. This value is close to the ion conductivity of the liquid electrolyte. On the other hand, this is superior to the ionic conductivity (10 ^-4 to 10 ^-3 S / cm) of the gel polymer electrolyte. Therefore, when a solid electrolyte, particularly a ceramic solid electrolyte, is used, there is no danger of electrolyte leakage in the liquid state, and there is no danger of explosion or ignition.

When the liquid electrolyte is replaced with a solid electrolyte, it can have advantages such as improvement of energy density and safety. However, solid electrolytes do not penetrate into the electrodes, unlike liquids, because they are solid, and can not make their own ion conduction paths inside the electrodes. Therefore, an electrode is formed by mixing solid electrolytes, and it is difficult to form a solid ionic conduction path in a solid state. Solving these interfacial problems is a major research topic of all solid state batteries in recent years.

When a gel polymer electrolyte is used for an electrode, unlike a solid electrolyte, since it has fluidity of a liquid, a smooth ion conduction path equivalent to a liquid or a liquid can be formed.

By using the solid polymer electrolyte and the gel polymer electrolyte in the electrode layer in the electrolyte layer, the advantage of the solid electrolyte can be utilized and the disadvantage of the solid electrolyte can be overcome.

The effects of the present invention are as follows.

1) it retains the advantage of choosing a solid electrolyte.

That is, the energy density can be improved because the lithium secondary battery is stable at a high temperature and a high pressure as compared with a liquid electrolyte, has excellent lifetime performance of the battery, and can be stacked in a stacked form.

2) solved the insufficient contact problem of the solid electrolyte inside the electrode of the pre-solid battery.

That is, the amount of contact between the electrolyte and the electrode material in the electrode is increased as compared with the technique using the conventional solid electrolyte, and the internal resistance of the electrode is decreased to increase the capacity of the battery.

As a result, it is possible to form electrodes of high loading and high density as compared with a technique using a conventional solid electrolyte thin film.

3) The capacity of the electrode increased through binder exclusion.

That is, since the gel polymer electrolyte can replace the role of the binder, the binder can be excluded, and thus the amount of the active material used can be increased, resulting in an increase in the battery capacity.

Claims (9)

1. A pre-solid secondary battery comprising a cathode, an anode, and a solid electrolyte stacked therebetween,
The electrode, which is either or both of a cathode and an anode, is composed of an active material, an electron conduction material, and a gel polymer electrolyte,
The gel polymer electrolyte is a gel-like polymer including an acrylate crosslinking agent, a carbonate-based or ether-based solvent, and a lithium salt, and is a physical crosslinking gel composed of i) one or two or more polymers by ionic bonding or hydrogen bonding, or ii) A chemical crosslinking gel formed by copolymerization of at least two kinds of polymers,
Wherein the active material and the electroconductive material are mixed and dispersed in the gel polymer electrolyte,
The electrode does not include a separate binder,
Wherein the solid electrolyte is a ceramic solid electrolyte having properties different from those of the gel polymer electrolyte. delete The pre-solid secondary battery according to claim 1, wherein the gel polymer electrolyte is a homogeneous gel or a heterogeneous gel. The method of claim 1, wherein the lithium salt is _{LiBF 4, LiClO 4, LiPF 6} , LiAsF 6, LiCF 3 SO 3, LiN (SO 2 CF 3) 2, LiN (SO 2 C 2 F 5) 2, LiC (SO ₂ CF ₃ ) ₂ and LiB (C ₂ H ₅ ) ₄ .
The battery according to claim 1, wherein the pre-solid secondary battery is a lithium sulfur secondary battery, the active material is sulfur, the electron conduction material is a carbon body, and the content of the gel polymer electrolyte in the electrode is 10 to 30% - Solid secondary battery. The pre-solid secondary battery according to claim 1, wherein the pre-solid secondary battery is a lithium ion battery, and the active material is LiCoO ₂ , LiNiO ₂ , LiNi _x Co _y Mn _z O ₂ , LiMe _x Mn _{1 -x} O ₄ , LiFePO ₄ , A carbon nanotube, a graphene, or a mixture of at least one of them, and the content of the gel polymer electrolyte in the electrode is 10 to 30% of the mass of the electrode, Solid secondary battery. The solid electrolyte of claim 1, wherein the solid electrolyte is selected from the group consisting of a NASICON-type, a Garnet-type, a Perovskite-type, a LiPON-type, Wherein the solid electrolyte is a Thio-LISICON-type. The pre-solid secondary battery according to claim 1, wherein the solid electrolyte is 10 to 1,000 占 퐉. The pre-solid secondary battery according to claim 1, wherein the electrode is cast to 100 to 200 탆.

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